RADIOCHEMICAL OXIDATION OF AN ETHYLENE-PROPYLENE-HEXADIENE TERPOLYMER

The gamma ray initiated oxidation of an ethylene-propylene-hexadiene t erpolymer (molar ratios 87/12/1) was studied by IR spectrophotometry i n the 40-90-degrees-C temperature range, with dose rates varying from 10 to 2500 Gy h-1 and integrated doses up to 100 kGy. Bulk (almost-equ al-to 8mm) and thin (almost-equal-to 0.1 mm) samples were studied. It appears that the oxidation is diffusion controlled in the bulk samples and non diffusion controlled in thin films. A kinetic study of IR spe ctral changes in these latter reveals that vinylene groups of the hexa diene monomer unit disappear in the early period of exposure, presumab ly by addition reactions with peroxy radicals. A very simplified mecha nistic scheme allows a satisfying modelling of this process whose rate is almost proportional to the dose rate (irradiation intensity).